(1) Field of the Invention
This invention relates to an epoxy resin composition, and more specifically, to an epoxy resin composition capable of giving a cured product having excellent pliability and a high glass transition temperature.
(2) Description of the Prior Art
Epoxy resin molding materials of the type in which an epoxy resin is cured by using a novolak-type phenolic resin are much used as, for example, a semiconductor encapsulating material since they are excellent in adhesiveness and moisture resistance. In the molding materials of this type, however, internal stresses occur owing to shrinkage during molding and curing. This leads to the disadvantage that as the chip size increases, cracks are formed in the resin or chips, and bonding wires undergo breakage.
It is known that as means for solving this problem, a flexibilizing agent such as silicone resins or polybutadiene is incorporated in the molding materials so as to lower the modulus of the encapsulating resin (to make it pliable). However, in this method, the glass transition temperature of the cured resin abruptly decreases, and its electrical characteristics in a high temperature region are degraded. It is difficult therefore to obtain molded products having high reliability. Another defect is that the mechanical strength of the cured product is reduced.